康德-拉普拉斯

1、Mapping Magnetic Field Structure in Star-forming Regions賴詩萍Oct 4, 2006, NTHU Phys Colloquium康德-拉普拉斯 星雲假說康德(1755年) - 原始星雲是由大小不等的固體微粒組成的“天體在吸引最強的地方開始形成”萬有引力使得微粒相互接近。拉普拉斯(1796年) - 形成太陽系的雲是一團巨大的灼熱的轉動著的氣體大致呈球狀。由於冷卻星雲逐漸收縮,星雲的中心部分凝聚成太陽 。 Star formation standard model Shu et al. 1987Shu et al. (1987)Star fo

2、rmation standard model P. AndreStarless Cores Barnard 68 - Jeans Mass (1928)GravitationThermal PressureWhy B is important in star formation?lRegulating star formation efficiencylObserved star formation efficiency is lowlTheoritical 200 M/year Observed 3 M/yearlB provides support inlStatic fieldslMHD

3、 waves (turbulence) lFacilitating gravitational collapselAngular momentum problem magnetic brakinglMagnetic flux problem - ambipolar diffusion (Ostriker, Gammie, & Stone 1999)22AsVclarge - random morphologyZeeman Effect Too Difficult!Polarization of Dust Emission: PBpPolarized Molecular Line Emi

4、ssion (the Goldreich-Kylafis Effect): PBp or PBp BVDust Polarization observations with BIMA W51 e1/e2Lai et al. (2001)Chrysostomou et al. (2002)Matthews et al. (2002)Lai et al. (2002)DR21(OH) JCMT vs. BIMA(B map)Lai et al. (2003) NGC1333 IRAS4A NGC1333 IRAS4A NGC1333 IRAS4ALai (2002)Girart, Rao, Mar

5、rone (2006)1.Field Strengths (the Chandrasekhar-Fermi Method)2.Mass-to-magnetic-flux Ratios3.Turbulent-to-magnetic-energy Ratios Field Strengths in the plane of skyUniform fields perturbed by MHD turbulence - Incompressible fluid - invariantSmall perturbation -Isotropic turbulence - BB 4Blosp Ostrik

6、er, Stone, & Gammie 2001ResultslBp 0.8 3.5 mG lM/B,p 0.1 4.9 critical mass-to-flux ratio turb 0.03 0.4 lSMA (the only working interferometer for now)lCARMA = BIMA + OVRO (?)lALMA! (wait at least 7 years)lZeeman measurements lHigh density (106 cm-3) - CNlYoung Cores CCS lLine polarizationALMA in 7 years廣告時間 “Star and Planet formation” Journal